XMM- Newton observed the Seyfert 1.9 galaxy NGC~4258 in December 2000 .
At energies above 2 keV a hard nuclear point source is resolved that can be fitted by a highly absorbed power-law spectrum ( N _ { H } = ( 8.0 \pm 0.4 ) \times 10 ^ { 22 } cm ^ { -2 } , photon index 1.64 \pm 0.08 ) with an unabsorbed luminosity of 7.5 \times 10 ^ { 40 } erg s ^ { -1 } in the ( 2–10 ) keV band .
No narrow iron K \alpha emission line is detected ( 90 % upper limit of equivalent width EW \sim 40 eV ) .
The nuclear emission flux was observed to remain constant over the observation .
A short archival Chandra observation taken in March 2000 further constrains the hard emission to a point source coincident with the radio nucleus .
A point source \sim 3″ southwest of the nucleus does not contribute significantly .
Spectral results of the Chandra nuclear source are comparable ( within the limited statistics ) to the XMM- Newton parameters .
The comparison of our iron line upper limit with reported detections indicates variability of the line EW .
These results can be explained by the relatively low nuclear absorption of NGC~4258 ( which is in the range expected for its intermediate Seyfert type ) and some variability of the absorbing material .
Reflection components as proposed to explain the large iron line EW of highly absorbed Seyfert 2 galaxies and/or variations in the accretion disk are however imposed by the time variability of the iron line flux .